Fluid operated continuously actuated reciprocating piston drive



United States Patent 72] Inventor Hermann Joseph Pennther 10 Zeppelinstr, 1, Saarbrucken, Germany [21] Appl. No. 785,023 [22] Filed Dec. 9, 1968 Continuation of application Ser. No. 558,176, May 17, 1966, abandoned. [45] Patented Nov. 17, 1970 [32] Priority May 20, 1965 [33] Germany [31] .St. 23,856

[54] FLUID OPERATED CONTINUOUSLY ACTUATED RECIPROCATING PISTON DRIVE 8 Claims, 10 Drawing Figs.

[52] 11.8. CI 91/306, 91/309, 91/313, 91/317, 91/319 [51] Int. Cl F011 25/06 [50] Field of Search... 91/306, 305cur, 304cur, 301cur, 309, 313cur, 3l7cur, 319cur [56] References Cited UNITED STATES PATENTS 553,261 1/1896 Reussner 91/309 688,598 12/1901 Caryell 91/306 728.283 5/1903 Officer et al 91/309 1,584,715 5/1926 Bayles 91/301 2,201,248 5/1940 Stone 91/309 2,296,647 9/1942 McCormick 1 91/306 3,094,902 6/1963 Riopelle 91/306 FOREIGN PATENTS 172,243 12/1921 Great Britain 91/304 Primary Examiner- Paul E. Maslousky Atrarney lohn J. Dennemeyer ABSTRACT: A double acting pressure booster having at least one reversing valve for reversing the pressure medium towards one or the other side of the low pressure piston wherein the reversing valve is reversed by a pressure difference created by ment of the slide member so that the valve is reversed positively also during the creeping movement of the low pressure piston.

Patented Nov. 17, 1970 3,540,348

Sheet 3 013 FLUID OPERATED CONTINUOUSLY ACTUATED RECIPROCATING PISTON DRIVE This is a streamlined continuation of application Ser. No. 558,176, filed May 17. 1966, now abandoned.

This invention relates to a hydraulically or pneumatically actuated piston drive with a reciprocating movement, and more particularly to a double acting booster in which the movements of the low pressure piston influence in the end positions the control pressure for the reverse operation. Although the invention is not limited to pressure boosters but may be applied in a similar manner to most embodiments, for example also for hydraulically or pneumatically actuated motors; the following description will be limited to double acting pressure boosters.

In the field of the double acting air compression motors it is known for the reverse operation, that the movements of the work piston reduce in the end positions the control pressure of an impulse regulator, Le. of a four-way valve regulated, by pressure release, into whose regulation chambers disposed on both sides of the control slide and in contact with the pressure source the control lines open.

In another type of air compression motor the usual three way pilot valves which are mechanically actuated by the work piston and which regulate the four-way valve have been replaced by simple two-way pilot valves so that the constant pressure impingement in the two regulation chambers of the four-way valve is provided by auxiliary bores in the control slide or in the valve body of the four-way valve instead of by the three-way pilot. valves. The bores connect the pressure source to the two regulation chambers of the four-way valve.

This arrangement has the disadvantage that it fails in case of a creeping travel of the work piston. The reason for this is that during very slow travel'the pilot valves also open very slowly so that the pressure release of the control chambers takes place very slowly in the end positions. The control slide'starts to travel slowly into the opposite end position and stops in its travel in the center position because the pressure difference is not sufficient to overcome the further resistance to its movement. Depending on the construction ofthe valve:

a. the pressure connection and both cylinder connections are closed off; or

b. the pressure connection is closed off and both cylinder connections are without pressure. The low pressure piston remains stationary and the pilot valves remain in the degree of aperture in which they happen to be at that moment.'

It is an object of the present-invention to provide for, in a continuous piston drives of the above mentioned type, a reversing delay by simple connecting means which, similar to the known quick break connection or throttling in control lines, prevents a stopping of thepiston drive'during creeping travel but which on the other hand does not impede the rapid travel which canoccur by a throttling in a control line.

The invention provides a solution in which two three-way valves of special construction may be regulated by pressure release as well as pressure impingement. According to the invention the reverse'actuation of a piston drive in which the reciprocating movements of the workpiston changes the control pressure in the end positions, by means of two hydraulically regulatedthree-way valves whose control slide has a differential piston with a smaller annular surface impinged constantly by the operating pressure and a greater surface on one face side of the control slide. The control chamber associated with the greater surface is connected on one side by a bore of small diameter in the control slide to the pressure source and on the other side to a control line. The bore of small diameter is blocked in the end position of the control slide in which the valve is regulated upwardly for the piston drive. A passage way in the control slide is maintained openthrough which, in case there is no pressure in the regulating chamber, a small leakage current flows. which builds up a preliminary pressure in the regulating chamber when the control line is blocked. In the outgoing line of each of the three-way valves to one of the working chambers of the piston drive opposite the associated control, line opposite pressure ratios are established. The bore of small diameter opens appropriately on a pistonlike projection of the greater control surface; and by contact of its auxiliary or sealing surface with the valve cover, blocks the bore up to a radial notch in its face surface. In this manner a preliminary pressure builds up in one end position by means of the leakage flow through the radial notch, When a predeter mined pressure is produced by the differential piston effect, a displacement of the control slide is initiated in a delayed manner until the remaining sealing surface is lifted fromthe valve cover anti is impinged additionally over the now fully open bore in the control slide which is connected to the pressure source. This sudden power difference at the differential piston produces a sudden reverse operation of the control slide.

The arrangement ofthe reversing valves according to the invention makes possible simplifications in the manner according to which the changes of the control pressure are initiated by the movement of the piston of the piston drive. These simplifications will be explained-hereafter in greater detail with reference to the attached drawings in which the invention is illustrated by means of diagrams showing several embodiments of double'acting hydraulic pressure boosters and in which:

FIGS. 1, 4, 5 and 7 show circuit diagrams having two three- 7 way valves according to the invention, each embodiment being different from the others as to the development of impulses for the reversing movements of the three-way valve,

FIGS. 2, 3 and 6 show details of the operating circuit of FIGS. 1,4,5 and 7, and

FIGS. 8 and 9 show sections of the three-way valves in two different control positions.

FIG. 10 shows details of the three-way valves of boosters, 8 and 9.

The continuous piston drive, shown in the embodiments, as hydraulic, double acting boosters, consists in a known manner according to FIG. I-ofa low pressure cylinder 20 in which the piston 21 divides the cylinder into two cylinder chambers 22 and 23, the high-pressure cylinders 24, 25 and the high-pressure pistons 26,27 which represent the piston rods in a motor drive. Thehigh pressure is introduced alternately through over check valves 28, 29 in the lines 30, 31 to the consumer station. Over check valves 32, 33 in the lines 34, 35 the highpressure pistons 26, 27 may take up pressure medium during their return strokes. The lines 34, 35 may be connected by two three-way valves 37, 38 (FIGS. 1,4,5 and 7) alternately to the pressure line 39 and the return line 40 to the reservoir or pressure-free area 41. Through the branches 42, 43 the cylinder chambers 22 and 23 of the low pressure cylinder 20 are alternately impinged and connected to the return flow. In this respect all the circuits are the same. Furthermore the condition of the individual chambers is indicated in all these circuits by reference letterp or 0 to indicate that they have a positive pressure p or a zero pressure 0.

Reference is now made to FIGS. 8 and 9 which illustrate the three-way valves 37, 38of special construction. Each of these valves consists of the valve housing with an inlet means IN, an-outlet means Cyl., an exhaust means OUT and the control connection 91. The control slide 92 which forms a differential piston, has two face side surfaces F1, F2 and the smaller annular surface FI-F2. The smaller annular surface FI-F2 and the larger ofthe face side surfaces FI, being designated as the greater surface, form opposed control surface means for effecting the reversing movements of the control slide 92. A pistonlike projection 92a extends from the greater surface Fl so as to subdivide the greater surface into two concentric surfaces, the innermost concentric surface being designated the auxiliary surface or sealing surface SI and the outer concentric surface being-designated as the first surface 50. The control slide 92 can assume two stable positions or end positions. If the control pressure pST 0, that is if according to FIG. 9 the control line 94 (FIG. I) is without pressure, the pressure p acting on the annular surface FIF2 urges the control slide 92 against the cover 95 of the control chamber 96. In that case the bore 97 with diameter a, which connects the annular surface Fl-F2 with F1, is closed by the auxiliary or sealing surface 51 of pistonlike extension 92a of the greater surface F1 on which the bore 97 opens. Into this sealing surface a small notch 52 is cut so that in this position a small leakage flow may escape over the pressure free control line 94.

The second position according to FIG. 8 is given when the control line 93 is under the pressure p ST p. As the two surfaces Fl =F2 and F1 are under the same pressure p the control slide 92 is pressed in the opposite end position wherein the now free bore 97 provides a pressure equalization in both chambers.

The circuit connections of these two positions are illustrated in FIGS. 1, 4, 5 and 7 by symbols in which the state of the connections are designated by the letter p and 0 to indicate that they have a positive pressure p or a zero pressure 0.

The reverse operation from the first end position of FIG. 9 (valve 38 in FIG. 1) into the second end position according to FIG. 8 is obtained by closing the control line 94. The leakage current flowing through the notch 52 in the sealing surface of the projection 92a causes a rapid pressure increase due to the small volume of the closed space. At the moment where the F1 F2 F1 the control piston is in an unstable equilibrium. Due to this the sealing surface is lifted and the medium flowing now thro'ugh the bore 97 pushes the control slide 92 with increased speed into the opposite, second end position.

The reversing operation from the second end position shown in FIG. 8 into the first end position shown in FIG. 9 takes place conversely by opening the control line 93. At the moment where the control pressure drops below the limit F1F2 Fl moves with increased speed into the other end position and displaces the fluid medium in the control chamber 96 and flowing through bore 97 during the switching operation until in the end position the bore 97 is again almost completely blocked by the auxiliary or sealing surface. It is important that in the control lines 93 or 94 and in the branches 42 or 43 to cylinder opposite pressure conditions always exist, i.e. if the control line 94 is without pressure the outgoing cylinder line 42 is under pressure or the reverse may be-the case. This is established by the connections 98, 99 (FIG. 9).

The reversing operation of the booster shortly before reaching an end position may be initiated by:

1. pressure relief of the control chamber of one of the two three-way valves 38, 37.

2. pressure impingement in the control chamber of one of the three-way valves.

The possibility mentioned under 1 above has been shown in FIG. 1. During the stroke of the piston 21 to the left the control chamber 96 of the three-way valve 38 and lines 94, 99, 43 are free of pressure while the control space 96 of the three way valve 37 and the lines 93, 98, 42 are under the pressure p. As the two associated two-way pilot valves 100 and 101 remain closed during the stroke due to spring pressure the lines 98, 99 assure that the above pressure conditions are maintained in that they connect the control spaces with those branches 42, 43 to the low-pressure cylinder 20 which have an equal potential. For example, as piston 21 moves to the left, cylinder chamber 23 is relieved of pressure through branch 43 which is connected with the reservoir of pressure-free area 41 via three-way 37. Branch 43 is also connected via control lines 99 and 94 to the control chamber 96 to maintain the control chamber pressure-free. At the same time cylinder chamber 22 receives pressure medium via branch 42 which is connected to the pressure source via three-way valve 38. Branch 42 is also connected via control lines 98 and 93 to control chamber 96 of valve 37 to maintain pressure in this control chamber.

The reversing operation in the left end position of the work piston 21 is obtained by mechanical actuation of the pilot valve 100 whereby the control chamber of the three-way valve 37 is relieved of pressure and the cylinder chamber 23 control pressure exceeds the value P value p the control slide 92 receives a pressure p. At the same time the control chamber of the three-way valve 38 is put under pressure through line 99 whereby this valve is reversed and the cylinder chamber 22 is relieved of pressure. After reversing the direction of movement the pilot valve 100 is returned by a spring pressure means into its rest position but the control line 98 provides that the control space of the three-way valve 37 receives no pressure until the next reversing operation. The two way pilot valves 100, 101 may be designed as shown in FIG. 2 wherein the spring pressure must in each case be larger than the pressure force acting against the opposite side of the piston. In place of the spring pressure a valve with return action by differential pistons according to FIG. 3 may be used.

If one employs in this arrangement the high pressure pistons 26, 27 for the reversing operation one obtains the circuit according to FIG. 4 in which the control chambers connected to the bores 104 are pressure relieved at the reversing points in that the annular grooves 105 milled into the high pressure 0 pistons 26, 27 provide the connection to the bores 106 which in turn are connected to the reservoir 41 or the pressure-free area.

The reversing operation by pressure impingement of the control space of one of the two three-way valves 37, 38 is illus- 5 trated in the circuit arrangement according to FIG. 5.

Pilot valves, or more specifically, impulse producers 208, 209, include in this case two pistons 108, 109 each provided with a spring return and an axial through-passage, these pistons being mechanically operated at the reversing points by 0 the low pressure piston 21 of the pressure booster. In this way the axial bore is first closed and thereafter the medium present in the cylinder 110 is compressed. A possible design ofthis impulse producer is shown in FIG. 6.

The control line 194 of the three-way pilot valve 38 which 5 feeds pressure to the cylinder chamber 22 is connected with cylinder 110 and the bored piston 108 of the impulse producer 208 to the now pressure-free cylinder chamber space 23 while the control line 193 of the three-way valve 37 which pressure relieves the space 23 is connected with the impulse producer 209 and its piston 109 to the chamber 22 which is under pressure. In this manner the positions of the three-way valves are blocked relative to each other. When toward the end of the stroke the piston 21 of the pressure booster strikes against the impulse producer 208 the associated control line 194 is closed off and with sufficient speed a pressure impulse is produced.

When this pressure impulse exceeds the value LFZL the control piston of the three-way valve 37 moves with increased speed into its opposite end position and thereby puts the space 23 under pressure whereby the direction of movement of the booster piston 21 is reversed. 0 When in the course of the reversed movement the axial bore of the impulse producer 208 is uncovered again no change occurs with respect to the control pressure because the cylinder chamber 23 as well as the control chamber 96 of the threeway valve 38 have the same pressure p.

If during a creeping movement the speed of the booster piston 21 is so small that after closing the axial bore of the piston 108 no sufficient pressure impulse occurs the leakage current flowing through the notch of the sealing surface 92a of 0 the three-way valve 38 is sufficient to charge its control chamber 96 sufficiently fast to the limit value to initiate thereby the reverse operation. A'further important simplification may be obtained here also in that the 75 high pressure pistons 26, 27 may be employed for the the piston rod. Projections 114, 115 of the high pressure pistons move into these annular chambersbefore they reach each respective end position and exactly the same reversing effects are obtained as in the previously described impulse producers.

lclaim:

l. A fluid operated continuously actuated reversing piston drive with reciprocating movement in which movements of a piston in cylinder chambers vary a control pressure in the end positions thereof for actuating valve means for sudden reversing action, comprising:

a. a valve means having two hydraulically controlled threeway valves each having an outlet means alternately delivering a pressure medium to one of said cylinder chambers for said reversing piston drive via branches;

b. a control slide within each of said three-way valves having a first and a second end position wherein said outlet means is alternately connected with an inlet means for transmitting working pressure to said one of said cylinder chambers of said piston drive in said first end position and with an exhaust means in said second end position;

c. each of said control slides defining a differential piston having different opposed control surface means for effecting the reversing movements of said control slides when exposed to pressure;

d. one of said opposed control surface means having a smaller annular shaped surface and being continuously exposed to the working pressure in both of said end positions of said control slides;

g. the other of said opposed control surface means having a greater surface being located on a face side of one of said control slides and subdivided into a first surface and an auxiliary surface which is ineffective in said first end position by a sealing cooperation with a valve cover;

f. said valve cover closing a control chamber disposed adjacent to said greater surface; and

control lines and pilot means being actuated by the movement of said piston effecting a pressure difference between said opposed control surface means causing at least a delayed movement of said control slide of one of said three-way valves when said control slide is in said first end position, whereby the area of said auxiliary surface is suddenly effectively added to the area of said first surface forcing said control slide into said second end position, said control slide of said other three-way valve being moved into its first end position.

2. A piston drive as defined in claim 1 wherein said control chamber of each of said three-way valves is connected on one side to said inlet means via a bore of small diameter in its respective control slide and connected on the other side to one of said control lines, said bore being closed in said first end position, in which position said three-way valve delivers a pressure medium to one of said chambers of said piston drive; a passageway maintained open allowing a small leakage flow for building up a preliminary pressure in said control chamber.

3. A piston drive as defined in claim 2 wherein said bore terminates in a pistonlike projection defining said auxiliary surface of said greater surface said projection closing said bore in said first end position by sealing contact with said valve cover, and further including a small notch in said auxiliary surface through which said leakage flow occurs.

4. A piston drive as defined in claim 1 wherein said threeway valves are regulated by means of a release of pressure from one of said control lines of one of said valves and the control line of said one valve being connected with one of said branches of the other of said valves.

5. A piston drive as defined in claim 1 further including a pair of two-way pilot valves arranged in said control lines of said three-way valves said pilot valves being closed in the rest position by a spring return means and opened in the end positions mechanically by said piston, wherein the pressure of said control chamber of the associated three-way valve releases into a pressure-free area.

6. A piston drive as defined in claim 1 including means for regulating said three-way valves by a pressure impingement through said control lines, said control lines being connected to said pilot means having impulse producers actuated mechanically in their end positions by said piston.

7. A piston drive as defined in claim 6 wherein said impulse producers each include cylinders mounted in said piston drive and having spring biased pistons.

8. A piston drive as defined in claim 6 wherein said impulse producers include annular chambers arranged concentrically relative to a pair of piston projection members attached to said pistons. 

